Hydrocarbons can be produced from wellbores drilled from the surface through a variety of subsurface formations. A wellbore may be substantially vertical or may be deviated. Conditions and other parameters in the wellbore can be sensed using powered devices downhole. For example, many parameters, such as pressure, temperature, fluid density, and fluid flow rate, may be sensed downhole and their values reported to the surface. Powering these devices electrically can be challenging in view of, among other things, temperature limitations of complex electronic sensors.